In recent years, fishermen have gathered each year off the coast of Taiji, Japan, to corral dolphins into a small cove to be killed for their meat or sold to aquariums around the world. The group Whale and Dolphin Conservation estimates that more than 18,000 dolphins have been killed or captured in Taiji since the year 2000.

Psihoyos has faith in the ability of documentary films to effect social change.

The hunt has taken place every year since 1969, but this year it met a different reception—one that suggests changing public attitudes toward the hunting and capture of dolphins. The U.S. ambassador to Japan, Caroline Kennedy, tweeted that she was "deeply concerned by inhumaneness of drive hunt dolphin killing," and added that the United States government opposes such hunts. German and U.K. officials made similar statements, while the artist Yoko Ono published an open letter.

"At this very politically sensitive time," Ono wrote, the hunt "will make the children of the world hate the Japanese."

And the difference wasn't just about the high-profile objections, says Naomi Rose, a marine mammal scientist with a Ph.D. in cetacean biology. This year's dolphin hunt reached the attention of a larger and more global audience than earlier hunts have done due to increased discussion in social media.

Louie Psihoyos, executive director of the nonprofit Oceanic Preservation Society and director of The Cove—the Oscar-winning documentary film that made the Taiji hunts famous when it was released in 2009—adds that this increased media attention is helping change the discussion around the hunting of whales and dolphins.

Psihoyos has faith in the ability of documentary films to effect social change. "I call them weapons of mass construction," he says. "You make a good documentary and it keeps rippling around the world. Our movie is five years old now; it's still doing its work."

A second, more recent, documentary film has reinvigorated the movement against the captivity of whales and dolphins. Blackfish, released in 2013, follows the life of the orca Tilikum, a performing animal at a SeaWorld theme park that was involved in the death of trainer Dawn Brancheau. The film documents the negative effects of a long life of captivity for orcas and enjoyed exposure to a large audience over 17 airings on CNN's broadcast network.

SeaWorld reacted defensively to the film. For example, a headline at the company's new "Truth About Blackfish" website reads "Why 'Blackfish' is Propaganda, not a documentary." SeaWorld goes on to say that the claims made in Blackfish are illegitimate because it relies on information from "animal rights activists masquerading as scientists" and "former SeaWorld employees, most of whom have little experience with killer whales." SeaWorld has also published full-page ads in several national newspapers to refute claims made by the film.

Rose says that she sees SeaWorld's reaction as a sign of hope.

"We've been bandying about in the advocacy circles this Gandhian idea: first they ignore you, then they laugh at you, then they fight you, then you win. SeaWorld is putting a lot of money into their PR," Rose says. "So next is the win."

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Andy Butter wrote this article for YES! Magazine, a national, nonprofit media organization that fuses powerful ideas with practical actions. Andy is an intern at YES!